Our general goal is to develop a broader understanding of the thermodynamics of ligand linked phenomena as exemplified in various respiratory proteins. Three classes of linkage control may be described: allosteric, where the protein structure changes: polysteric, where polymerization of protein occurs; and polyphasic, where phase changes take place. The properties of these systems are sensitive to solution conditions, various reaction ligands, and temperature. In order to explore the wide range of phenomena encountered, a variety of experimental techniques for determination of binding curves, specific ion reactions, heats of reaction, and water activity are being used. Our research goals for the coming year are to: 1. Continue phase diagram investigations of HbS as a function of anti-cycling compound concentration, pH (Bohr effects of gelation), and temperature. Examine gelation properties in whole cells. 2. Place the new small volume (0.5 cc) calorimeter into full operation with computer data acquisition and analysis. Determine heats of ligand binding of O2 to trout I hemoglobin and hemocyanins in collaboration with Prof. Brunori of Rome. 3. Investigate the effect of oxygen ligation on the water activity of hemoglobin gels (HbS) and crystals (HbA) by means of osmometry and solubility studies. 4. Complete book with Jeffries Wyaman on thermodynamics of macromolecular ligand processes.